A pressure sensor detects pressure on the basis of a resistance change of a gauge resistor in accordance with a load, which is directly transmitted to the gauge resistor. Here, the pressure as a measurement object distorts a diaphragm, and then, the distortion of the diaphragm is directly transmitted to the gauge resistor as the load through a load transmission member. This type pressure sensor is disclosed in, for example, U.S. Pat. No. 5,349,873.
In the above sensor, when the load applied to the sensor is relatively small, the resistance change is small. Therefore, in this small load region, the sensor shows a small sensitivity so that the sensor does not detect the pressure precisely. Further, the characteristic curve of the sensor, which shows a relationship between the load and the resistance change, is not straight so that the curve does not have sufficient linearity. Furthermore, the curve may have a hysteresis loop. Thus, the pressure sensor does not have sufficient sensitivity and detection accuracy.